The Baltimore Longitudinal Study of Aging (BLSA) is an ongoing, multidisciplinary research project aimed at understanding the aging process in men and women. Longitudinal changes are assessed by having a cohort of community-dwelling subjects of both sexes and ages across the adult life span, who return at variable intervals from 1-5 years, depending upon age, for a comprehensive evaluation. Major goals of the study are: 1) to better understand age-related changes in various organ systems and their inter-relationships; 2) to characterize the transition from normal to pathological aging, and 3) to relate functional changes in these systems to the development of specific diseases and mortality. The purposes of the BLSA are fourfold: 1) to obtain repeated measures of physiological, pathological, biochemical, and psychological variables on longitudinal study participants; 2) to compare levels of function repeatedly measured in age and sex cohorts; 3) to follow changes in individual participants up to and beyond age-related endpoints and disease events; and 4) to identify characteristics of individual participants that may be markers of biological aging, and to analyze their influence on clinical outcomes. Cross-sectional characterization of multiple parameters is also obtained and differences related to age, sex and race are quantified. Aging, secular and period effects are examined. Relationships between such variables as nutritional habits, customary levels of physical activity, and adaptations to age-associated physical diability with glucose metabolism, cardiovascular function and specific disease outcome are being examined. Studies of some BLSA participants are conducted on the GCRC, Johns Hopkins Bayview Medical Center, and include assessments of nutritional patterns and oral glucose tolerance testing.